People cannot live and work without electricity. If without electricity, the world will be unimaginable, life will be tedious or uninteresting, and the production will be stagnated to directly cause collapse of the whole society productivity. Electrical energy is so important that countries all over the world pay considerable attention to the development of electrical energy at present. Common power generation includes wind power generation, hydroelectric generation, thermal power generation and nuclear power generation, where the thermal power generation and the nuclear power generation are being abandoned gradually now because they cause substantial pollution and do not meet the requirements of human development, while the hydroelectric generation has few resources and is far from sufficient to meet people's demands for electricity. Therefore, the clean and environmentally friendly wind power generation, with rich resources, becomes a main direction of development in future.
At present, large vertical-axis wind generators using grid-connected power generation still have many problems, and these problems are all caused by the unstable factors of natural wind. At a low wind speed, the large vertical-axis wind generators are difficult to start or simply cannot be started, as a result, resources are wasted by generators; at a normal wind speed, although the large vertical-axis wind generators can be started to work, the generators have low power generation efficiency and are often not in full-capacity state; and at an ultrahigh wind speed, the rotation speed of the generators is quickened obviously, even beyond the rated power of the generators, in this case, the generators are in risk of damage and components thereof are likely to be damaged, meanwhile, ultrahigh power output may cause hazards. In addition, as the natural wind is constantly changing in speed, i.e., a small wind speed, a low wind speed or a high wind speed, the power generated by the generators is extremely unstable, which will impact on the power grid when the generators are connected thereto.
The current power supply system in China works as follows: transformer substations supply electricity generated by the power generation equipment to power distribution stations in each area, and then the power distribution stations supply electricity to residents and factories in this area. However, for remote areas, grid-connected power supply results in problems of high cost, inconvenient maintenance and the like, further results in difficult electricity supply to remote areas. This has become a problem urgent to be solved by governments at all levels at present. Off-grid power generation is undoubtedly the best way to solve this problem. Therefore, how to utilize wind power generation to solve this problem has become a direction of research and development.
No matter for grid-connected wind power generation or off-grid wind power generation, people have high demands on electricity for production activities in daylight, so transformer substations are in quite short supply of electricity, sometimes even supply electricity area by area to ease the shortage of electricity; while as people have low demands on electricity for production activities in night, the transformer substations have surplus electricity which however cannot be utilized in people's production activities and lives and is thus wasted. Therefore, how to utilize the wasted part of electricity is another problem to be solved for wind generators in grid-connected or off-grid generation.